Benchmark Thermodynamic Properties of Methyl- and

Article pubs.acs.org/JPCA

Benchmark Thermodynamic Properties of Methyl- and Methoxybenzamides: Comprehensive Experimental and Theoretical Study Vladimir N. Emel’yanenko,† Ksenia V. Zaitseva,† Ruslan N. Nagrimanov,‡ Boris N. Solomonov,*,‡ and Sergey P. Verevkin*,† †

Department of Physical Chemistry and Department “Science and Technology of Life, Light and Matter”, University of Rostock, Dr-Lorenz-Weg 1, D-18059, Rostock, Germany ‡ Department of Physical Chemistry, Kazan Federal University, Kremlevskaya str. 18, 420008 Kazan, Russia S Supporting Information *

ABSTRACT: The enthalpies of formation of 2-, 3-, and 4-CH3-benzamide, as well as for 2-CH3O-benzamide, were measured by using combustion calorimetry. Vapor pressures of the isomeric CH3- and CH3O-benzamides were measured by using the transpiration method. The enthalpies of sublimation/vaporization of these compounds at 298 K were obtained from temperature dependencies of vapor pressures. The enthalpies of solution of the isomeric CH3- and CH3O-benzamides were measured with solution calorimetry. The enthalpies of sublimation of m- and psubstituted benzamides were independently derived with help of a solution calorimetry-based procedure. The enthalpies of fusion of the CH3-benzamides were derived from differential scanning calorimetry measurements. Thermochemical data on CH3- and CH3O-benzamides were collected, evaluated, and tested for internal consistency. A simple incremental procedure was suggested for a quick appraisal of vaporization enthalpies of substituted benzamides. The high-level G4 quantum-chemical method was used for mutual validation of the experimental and theoretical gas-phase enthalpies of formation. A remarkable ability of the G4-based atomization procedure to calculate reliable enthalpies of formation was established for the set of aliphatic and aromatic amides. An outlook for the proper validation of the G4-AT procedure was discussed. mol−1. The latest G4 method from this series was found to have a mean absolute deviation of 3.5 kJ·mol−1 tested with 483 molecules of different structures and sizes in the G3/05 test set.3 However, it has been reported that the G4 method underestimates the ΔfHm ° (g, 298 K) values for most nitrocontaining compounds, by up to 10−20 kJ·mol−1,4−6 when using the atomization reaction for converting H298 enthalpies to gasphase enthalpies of formation. A significantly better agreement with experiment can be achieved when different isodesmic or homodesmic reactions are used, instead of the simple atomization procedure. However, it is well-established that the isodesmic reactions approach can be successful only if the experimental ΔfH°m (g, 298 K) values for the “anchoring” molecules are of a benchmark quality. Thus, there is a clear ° demand for expanding current databases with anchoring ΔfHm (g, 298 K) values, comprehensively validated so that results based on them can be relied upon.6 In our opinion, a reasonable criterion for evaluation of thermochemical data would be met if consistent experimental values are measured independently with at least two different techniques or in two different laboratories.

1. INTRODUCTION Amide and related functional groups are responsible for the interand intramolecular linkages in proteins and peptides as well as in synthetic polymers. The energetics of these types of bonds are important for understanding and prediction of reaction pathways and modeling of chemical and biochemical processes. Standard molar enthalpies of formation ΔfH°m, standard molar enthalpies of sublimation ΔgcrH°m, and standard molar enthalpies of fusion ΔlcrH°m exhibit a fundamental set of thermodynamic data required for quantification of the molecular energetics. Combination of experimental thermochemical methods with theoretical highlevel quantum-chemical calculations seems to be the most promising way for creation of reliable thermodynamic data sets for biologically relevant molecules.1,2 In this context, benzamide and its functional substituted derivatives represent a series of key C,H,N,O-containing compounds with structures relevant to biomolecules. Extended experimental and theoretical studies of these compounds have at least three advantages: they are commercially available, easy to purify for thermochemical measurements, and they are optimal in size for computing their energetics within a reasonable time with help of the highlevel quantum-chemical methods. Composite methods from the Gaussian-n family are widely used because of their “chemical accuracy” at the level of ±5.0 kJ· © XXXX American Chemical Society

Received: August 9, 2016 Revised: October 4, 2016

A

DOI: 10.1021/acs.jpca.6b08027 J. Phys. Chem. A XXXX, XXX, XXX−XXX

Article

The Journal of Physical Chemistry A

Figure 1. Compounds studied in this work: 2-CH3-benzamide, 3-CH3-benzamide, 4-CH3-benzamide, and 2-CH3O-benzamide, 3-CH3O-benzamide, 4CH3O-benzamide.

bubble meter used for measurement of the gas flow. The volume of the carrier gas VN2 was determined from the flow rate and the time measurement. Detailed results from transpiration experiments are given in Table S2. 2.3. High-Precision Solution Calorimetry. Solution enthalpies of 3-CH3-benzamide, 4-CH3-benzamide, 3-CH3Obenzamide, and 4-CH3O-benzamide were measured at T = 298.15 ± 0.01 K in concentration range from 1.3 to 9.3 mmol kg−1 using a solution calorimeter TAM III. Substituted benzamides were dissolved in the glass cell filled with 100 mL of acetonitrile by breaking a glass ampule containing ∼0.01−0.07 g of the compound under study. The verification of the calorimetric procedure was performed by measuring the reference solution enthalpy of NaCl in water.13 Details on the calorimetric procedure have been published elsewhere.14,15 Solution enthalpies of substituted benzamides measured in acetonitrile are listed in Table S3. 2.4. High-Precision Combustion Calorimetry. The molar enthalpies of combustion of 2-CH3-benzamide, 3-CH3-benzamide, 4-CH3-benzamide, 3-CH3O-benzamide, and 4-CH3Obenzamide were measured with an isoperibolic calorimeter with a static bomb and a stirred water bath. Details on the calorimetric procedure were published elsewhere.16,17 In a series of preliminary experiments with both CH3- and CH3O-benzamides, that complete combustion could easily be achieved with aid of small pieces of polyethylene. Samples pellets of mass ∼0.4−0.8 g were placed in the platinum crucible together with a small amount of auxiliary material and were burned in oxygen at a pressure of 3.04 MPa. The energy equivalent εcalor of the combustion calorimeter was determined with a standard reference sample of benzoic acid from NIST (sample SRM 39j). The combustion products were examined for carbon monoxide (Dräger tube) and unburned carbon, but neither was detected. We used conventional procedures18 for the reduction of the combustion results to standard conditions. Correction for nitric acid formation was based on titration with 0.1 mol·dm−3 NaOH (aq). Auxiliary data for combustion experiments are given in Table S4. Primary results from combustion experiments are collected in Tables S5−S8. 2.5. Differential Scanning Calorimetry Measurements. Enthalpies of Fusion. We used a differential scanning calorimeter (DSC) Mettler Toledo 822 to study thermal behavior of 2-CH3-benzamide, 3-CH3-benzamide, and 4-CH3benzamide by heating with a rate of 10 K·min−1 from room temperature to temperatures of ∼40 K higher than the melting

Joint treatment of the mutually consistent thermochemical results for compounds of interest can lead to the benchmark quality data sets, which can be recommended as reference materials for different thermochemical measurement or calculations. An experimental and computational study of the CH3- and CH3O-substituted benzamides presented in Figure 1 were performed, aimed at evaluation of the thermochemical data set of the benchmark quality to be useful for testing of quantumchemical methods as well as suitable as the reference or anchoring molecules for the isodesmic approach. This paper complements our previous work on thermochemistry of amides and compounds with related functional groups.7,8

2. MATERIALS AND METHODS 2.1. Materials. Commercial samples of benzamide derivatives (Table S1) with the purity 98−99% were additionally purified by fractional sublimation in vacuum. No impurities (greater than 0.001 mass fractions) were detected in samples used for the thermochemical measurements. The degree of purity was determined using a gas chromatograph (GC) equipped with an HP-5 capillary column with a column length of 30 m, an inside diameter of 0.32 mm, and a film thickness of 0.25 μm. The standard temperature program of the GC was T = 333 K for 180 s followed by a heating rate of 0.167 K·s−1 to T = 523 K. 2.2. Vapor Pressure Measurements. Transpiration Method. Absolute vapor pressures of 2-CH3-benzamide, 3CH3-benzamide, 4-CH3-benzamide, and 2-CH3O-benzamide, 3CH3O-benzamide, 4-CH3O-benzamide were measured by using the transpiration method.9−12 Small glass beads were covered with the sample under study and placed in a saturator. At a constant temperature (±0.1 K) a nitrogen stream was passed through the saturator. The transported material was collected in a cold trap at 243 K. The GC was used to determine amount of the sample condensed in the cold trap. The vapor pressure pi at each temperature Ti was calculated from the amount of the product collected within a definite period. Vapor pressures pi of a substance i were calculated with eq 1: pi = mi ·R ·Ta /V ·Mi ;

V = VN2 + Vi

(VN2 ≫ Vi )

(1)

where R is the universal gas constant; mi is the mass of the transported compound, Mi is the molar mass of the compound, Vi its volume contribution to the gaseous phase, VN2 is the volume of the carrier gas, and Ta is the temperature of the soap B


Article

The Journal of Physical Chemistry A Table 1. Enthalpies of Sublimation ΔgcrH°m of Benzamides (in kJ·mol−1) compounds benzamide (cr) 2-CH3-benzamide (cr)

Ma

ΔgcrHm ° /Tav

T range/K

K T

325.1−347.2 329.4−371.3

105.1 ± 0.3 105.2 ± 0.3

3-CH3-benzamide (cr)

K T SC

325.1−347.2 329.7−371.2 298.15

106.8 ± 0.4 105.1 ± 0.3

4-CH3-benzamide (cr)

K T SC

339.1−361.2 343.9−371.5 298.15

108.4 ± 0.4 107.2 ± 0.3

2-CH3O-benzamide (cr)

K T

335.1−357.2 368.4−398.5

109.9 ± 0.4 107.4 ± 0.5


K T SC

345.1−371.2 372.3−404.4 298.15

118.0 ± 0.4 117.5−0.6


K T SC

357.1−379.2 356.2−378.3 298.15

117.1 ± 0.4 116.3 ± 0.7

ΔgcrHm ° /298 Kb

ref

102.7 ± 0.4 106.1 ± 0.9 106.9 ± 0.6 106.7 ± 0.5 107.8 ± 0.9 106.6 ± 0.7 107.4 ± 1.0 107.1 ± 0.5 109.8 ± 1.0 108.9 ± 0.9 108.6 ± 1.1 109.1 ± 0.6 111.6 ± 1.0 110.4 ± 1.0 111.0 ± 0.7 120.1 ± 1.0 120.6 ± 1.1 120.1 ± 1.0 120.2 ± 0.6 119.6 ± 1.2 118.8 ± 1.3 118.2 ± 1.0 118.9 ± 0.6

27 24 this work averagec 24 this work this work averagec 24 this work this work averagec 25 this work averagec 25 this work this work averagec 25 this work this work averagec

a

Methods: K = Knudsen effusion method; T = transpiration method; SC = solution calorimetry based results (see text). bUncertainties in sublimation enthalpies are expressed in this table as standard deviations. Vapor pressure available in the literature were treated using eqs 2 and 3 to evaluate enthalpy of sublimation at 298.15 K in the same way as our own results. cAverage values were calculated using the uncertainty of the experiment as a weighing factor. Recommended values are given in bold.

group-additivity procedure.23 Primary experimental results on vapor pressures measured in this work are collected in Table S2. Vapor pressures of CH3-benzamides and CH3O-benzamides measured in this work are in very good agreement with results measured with the mass loss Knudsen effusion method24,25 (see Figures S1−S6). Taking this very good agreement into account, all available experimental data were additionally treated together using the Clarke and Glew26 equation to develop correlations accurately describing the vapor pressures of benzamides over a broad temperature range (see Table S10):

point. The DSC measurements were repeated in triplicate, and values agreed within the experimental uncertainties u(ΔlcrHm) = 0.5 kJ·mol−1 for the enthalpy of fusion and u(T) = 0.5 K for the melting temperature (defined as an onset temperature of the melting peak). The DSC was standardized using the highly purified indium. 2.6. Computational Details. We used the G4 method3 from the Gaussian 09 series software19 for calculations of energies and enthalpies of substituted benzamides. Details on computational procedure were reported elsewhere.20 The enthalpies, H298, of each compound were computed using the standard thermodynamic procedures.21

⎛ p⎞ Δg G ◦ (θ ) ⎛1 1⎞ R ·ln⎜ 0 ⎟ = − cr m + Δcrg Hm◦ (θ )⎜ − ⎟ ⎝ θ θ T⎠ ⎝p ⎠ ⎡θ ⎛ T ⎞⎤ ◦ + Δcrg Cp,m (θ )⎢ − 1 + ln⎜ ⎟⎥ ⎝ θ ⎠⎦ ⎣T

3. RESULTS AND DISCUSSION 3.1. Absolute Vapor Pressures from The Transpiration Method. Vapor pressures for 2-CH3-benzamide, 3-CH3benzamide, 4-CH3-benzamide, 2-CH3O-benzamide, 3-CH3Obenzamide, and 4-CH3O-benzamide were measured over the crystalline phase. Absolute vapor pressures pi were fitted with eq 2:9 R ·ln pi = a +

⎛T ⎞ b ◦ + Δcrg Cp,m ·ln⎜ ⎟ T ⎝ T0 ⎠

(3) o

where p is the vapor pressure at the temperature T, p is an arbitrary reference pressure (po = 1 Pa in this work), θ is an arbitrary reference temperature (in this work we use θ = 298 K or θ was an average temperature of the experimental range), R is the molar gas constant, ΔgcrG°m(θ) is the difference in the standard molar Gibbs energy between the gaseous and the crystalline phases at the selected reference temperature, ΔgcrHm ° (θ) is the difference in the standard molar enthalpy between the gas and the solid phases, and ΔgcrC°p,m(θ) is the difference in the molar heat capacity at constant pressure between the gaseous and the solid phase. An advantage of eq 3 is that the fitting coefficients of the Clarke and Glew equation (in contrast to coefficients of eq 2) are directly related to the thermodynamic functions of sublimation. Using the selected vapor pressures data sets (see Table S10) for each compound and ΔgcrCp,m ° (298 K) from Table S9, thermodynamic functions of sublimation were derived (see

(2)

where a and b are adjustable parameters. The ΔgcrC°p,m value is the difference between molar heat capacities of the gaseous and the condensed phase, respectively. T0 appearing in eq 2 is an arbitrarily chosen reference temperature (T = 298 K was chosen in this work), and R is the ideal gas constant. Values of ΔgcrC°p,m in eq 2 were calculated (see Table S9) according to the empirical procedure developed by Chickos and Acree22 based on the isobaric molar heat capacities C°p,m (cr, 298 K) estimated by the C


Article

The Journal of Physical Chemistry A Table 2. Solution and Solvation Enthalpies of Benzamides in Acetonitrile and Their Sublimation Enthalpies at 298 K compound (Ai)

ΔsolnHAmi/CH3CN a kJ·mol−1

ΔsolnHAmi/CH3CN b kJ·mol−1

ΔgcrHAmi c kJ·mol−1

3-CH3-benzamide 4-CH3-benzamide 3-CH3O-benzamide 4-CH3O-benzamide

24.6 ± 0.2 25.8 ± 0.5 28.2 ± 0.2d 26.3 ± 0.3

82.8 ± 1.0 82.8 ± 1.0 91.9 ± 1.0 91.9 ± 1.0

107.4 ± 1.0 108.6 ± 1.1 120.1 ± 1.0 118.2 ± 1.0

a

Enthalpy of solution of substituted benzamides in acetonitrile at 298 K (from Table S3). bEnthalpy of solvation of substituted benzamides in acetonitrile at 298 K. cSublimation enthalpies of substituted benzamides calculated according to eq 6. dEnthalpies of solution of substituted benzamides in acetonitrile (primary data are given in Table S3). eSolution enthalpy taken from ref 31.

Table 3. Thermochemical Data at T = 298 K for Benzamides (in kJ·mol−1)a compound Ai benzamide 2-CH3-benzamide

3-CH3-benzamide

4-CH3-benzamide

2-CH3O-benzamide

3-CH3O-benzamide 4-CH3O-benzamide

ΔfHm ° (cr)

ΔgcrHm °b

−202.5 ± 0.5 −234.3 ± 1.8f −239.1 ± 3.3g -235.4 ± 1.6h −240.2 ± 1.8f −239.4 ± 2.6g −239.9 ± 1.5h −244.2 ± 1.7f −248.4 ± 2.2g −245.8 ± 1.4h −365.6 ± 1.6h −368.2 ± 2.3g −366.5 ± 1.3h −375.5 ± 1.6i −376.3 ± 1.7i d

ΔfHm ° (g)exp

ΔfHm ° (g)c

−99.8 ± 0.6

−98.9e

106.7 ± 0.5

−128.7 ± 1.7

−127.8

107.1 ± 0.5

−132.8 ± 1.6

−132.8

109.1 ± 0.6

−136.7 ± 1.5

−133.1

111.0 ± 0.7 120.2 ± 0.6 118.9 ± 0.6

−255.5 ± 1.5 −255.3 ± 1.7 −257.4 ± 1.8

−256.6 −256.5 −256.5

102.7 ± 0.4

d

a

Uncertainties are expressed as twice the standard deviation. Values given in bold are recommended for thermochemical calculations. bEnthalpies of sublimation from Table 1. cCalculated with the G4 method by using eq 12. dTaken from ref 38. eCalculated with the G4 method according to the atomization procedure. fTaken from ref 24. gThis work. hWeighted average value. iTaken from ref 25.

Enthalpies of sublimation ΔgcrH°m of substituted benzamides available in the literature24,25 were adjusted to the reference temperature 298 K in the same way as our own results using eqs 2 and 4 with the heat capacity differences listed in Table S9 and calculated ΔgcrH°m(298 K) for the sake of comparison with our results (see Table 1). 3.3. Enthalpy of Sublimation Derived from Solution Calorimetry. We have shown recently28−34 that solution calorimetry serves as a complementary indirect method for determination of sublimation/vaporization enthalpies of organic molecules by using solution enthalpies measured at the reference temperature 298 K. It has been established that the molar solution enthalpy ΔsolnHAmi/S of a solute Ai in a solvent S and a molar solvation enthalpy ΔsolnHAi/S m of Ai in the same solvent S are ° by eq 6: connected to the molar enthalpy of sublimation ΔgcrHm

Table S11), and they can be further used for interpolations or reasonable extrapolations to calculate vapor pressures of the substituted benzamides under study. 3.2. Thermodynamics of Sublimation Measured by Transpiration Method. Enthalpies of sublimation of substituted benzamides at temperature T were derived from the temperature dependence of vapor pressure (see eq 4) using the following equation: ◦ Δcrg Hm◦ (T ) = −b + Δcrg Cp,m ·T

(4)

Entropies of sublimation at temperature T were also derived from the temperature dependence of vapor pressures using eq 5: Δcrg Sm◦ (T ) = Δcrg Hm◦ /T + R ·ln(pi /p°)

(5)

Experimental vapor pressures, coefficients a and b of eq 2, as well as values of ΔgcrHm ° (T) and ΔgcrSm ° (T), are listed in Table S2 and Table 1. Transpiration experiments with 2- and 3-CH3O-benzamides were additionally performed with liquid samples. Equations 2 and 4 are also valid for the treatment of the vapor pressure temperature dependence measured over the liquid, giving the standard molar enthalpy of vaporization Δgl H°m(T) and the ° (T). In this case in eqs standard molar vaporization entropy ΔgcrSm 2 and 4 we used the value Δgl Cp,m ° (see Table S9) instead of ΔgcrC°p,m. Combined uncertainties of the vaporization/sublimation enthalpies includes uncertainties arising from experimental conditions and uncertainties in vapor pressure, and uncertainties in the temperature adjustment to T = 298 K were calculated as described elsewhere.11,12

Δcrg Hm◦ (Ai , 298K) = Δsoln HmAi / S(298K) − Δsolv HmAi / S(298K)

(6)

This equation is also valid for the determination of vaporization enthalpies.28 Solution enthalpy is precisely measured using solution calorimetry (see Table S3). Solvation enthalpy can be calculated either using molar refraction28−30,33,34 or by a groupcontribution method.31,32 In the present work the solvation enthalpies were calculated according to the group-contribution method:31 Δsolv HmAi/S(298K) = Δsolv HmArH/S(298K ) + n × Δsolv HmX → H/S(298K) D

(7)


Article

The Journal of Physical Chemistry A Table 4. Thermodynamics of Phase Transitions in Benzamides (in kJ·mol−1) compounds 1

Tfus, K

ΔlcrHm ° at Tfus

ΔlcrHm ° /Tfus a 4

2

3

2-CH3-benzamide

415.1 414.9

3-CH3-benzamide

366.7 365.9

4-CH3-benzamide

433.2 432.8

2-CH3O-benzamide 3-CH3O-benzamide 4-CH3O-benzamide

401.7 407.2 440.6

22.9 ± 0.2e 21.6 ± 0.5f 22.7 ± 0.2g 21.6 ± 0.1e 20.8 ± 0.6f 21.5 ± 0.2g 24.3 ± 0.2e 25.8 ± 0.6f 24.5 ± 0.2g 27.2 ± 0.3h 28.6 ± 0.2h 29.0 ± 0.3h

0.055

0.059

0.057 0.068 0.070 0.066

ΔlcrHm °b

ΔgcrHm °c

Δgl Hm °d

5

6

7

106.7 ± 0.5

90.7 ± 1.5

107.1 ± 0.5

89.5 ± 0.9

109.1 ± 0.6 111.0 ± 0.7 120.2 ± 0.6 118.9 ± 0.6

91.4 ± 1.7 89.4 ± 1.8 97.5 ± 1.9 97.6 ± 2.4

16.6 ± 1.9 15.3 ± 2.0 16.0 ± 1.4g 17.9 ± 1.1 17.1 ± 1.3 17.6 ± 0.8g 17.0 ± 2.2 18.5 ± 2.3 17.7 ± 1.6g 21.6 ± 1.7 22.7 ± 1.8 21.3 ± 2.3

Empirical constant of the Walden’s rule:39 ΔlcrH°m/Tfus = const. bThe experimental enthalpies of fusion ΔlcrH°m measured at Tfus and adjusted to 298.15 K (see Supporting Information). cRecommended values taken from Table 1. dCalculated as the difference between (columns 6 and 5 in this table). eFrom ref 24. fThis work. gWeighted average value. hFrom ref 25. a

formation in the crystalline state ΔfHm ° (cr) (see Table 3). Values of Δcu° and ΔcH°m refer to reactions:

where ΔsolnHAi/S is the solvation enthalpy of the aromatic m compound in the solvent S; ΔsolnHArH/S is the solvation enthalpy m of the parent reference molecule in the same solvent S; ΔsolnHX→H/S is the contribution to the solvation enthalpy related m to the substitution of a hydrogen atom in the reference molecule with the substituent X; n is the number of substituents. Solvation enthalpies calculated by group additivity have been shown to be in good agreement with experimental solvation enthalpies available for aromatic compounds and their derivatives.31 Calculations of solvation enthalpies of CH3- and CH3Obenzamides were based on solvation enthalpy of benzene in acetonitrile (32.2 kJ·mol−1) and the group contributions for substituents: CH3− (3.3 kJ·mol−1), CONH2−(47.3 kJ·mol−1), and CH3O− (12.4 kJ·mol−1), reported previously.31 Solvation enthalpies of benzamides are presented in Table 2. Solution enthalpies of substituted benzamides in acetonitrile at 298 K required for eq 6 are given in Table S3. Sublimation enthalpies of substituted benzamides at 298 K were calculated according to eq 6 and given in Tables 1 and 2 for comparison with those derived by the conventional methods. It is apparent from Table 2 that sublimation enthalpies ΔgcrH°m(298 K) derived with help of the solution calorimetry are in agreement (within the combined experimental uncertainties) with those measured by the conventional methods (Knudsen and transpiration). With such good agreement, solution calorimetry is emerging as a valuable tool for an independent assessment of sublimation enthalpies. Moreover, in contrast to the conventional methods where the sublimation enthalpy is usually measured at elevated temperatures, the complementary solution calorimetry-based method provides values directly at the reference temperature 298 K. As a consequence, this way overcomes a lot of ambiguity expected from the adjustment of the ΔgcrHm ° (T) to the reference temperature specific for the conventional methods. We believe that the combination of the solution calorimetry-based method with the traditional techniques allows for mutual validation of available ΔgcrH°m(298) values. 3.4. Enthalpies of Formation from Combustion Calorimetry. The standard specific energies of combustion Δcu°(cr) of CH3- and CH3O-benzamides were measured with combustion calorimetry, and they are given in Tables S5−S8. These values were used to obtain the standard molar enthalpies of combustion ΔcH°m(cr) and the standard molar enthalpies of

C8H 9NO(cr) + 9.75O2 (g) = 8CO2 (g) + 4.5H 2O(l) + 0.5N2(g)

(8)

C8H 9NO2 (cr) + 9.25O2 (g) = 8CO2 (g) + 4.5H 2O(l) + 0.5N2(g)

(9)

Values of ΔfHm ° (cr) of CH3- and CH3O-benzamides were derived according to Hess’s Law10 applied to eqs 8 and 9 using reference values for the standard molar enthalpies of formation of CO2(g) ΔfHm ° (g) = −393.51 ± 0.13 kJ·mol−1 and H2O(l) Δ fHm ° (l) = −285.83 ± 0.04 kJ·mol−1 assigned by CODATA.35 The well-established procedure17 was used to calculate uncertainties related to combustion experiments. The uncertainties assigned to the standard molar energy of combustion correspond to expanded uncertainties of the mean (0.95 confidence level). The uncertainty assigned to the molar enthalpy of combustion and uncertainty assigned to the molar enthalpy of formation is twice the overall standard deviation. The latter uncertainty includes the uncertainties from the combustion energies of the auxiliary materials, uncertainty from calibration, the uncertainties of the enthalpies of formation of the reaction products H2O and CO2,36 as well as the uncertainty due to the specific intervals of atomic masses reported by IUPAC.37 The solid-state standard molar enthalpies of formation of 2-, 3-, and 4-CH3-benzamides measured in this work (see Table 3) are in an agreement (within the combined uncertainties) with the previous results measured with the isoperibolic static bomb calorimeter without using the auxiliary compounds to achieve completeness of combustion.24 Also the solid-state standard molar enthalpy of formation 2-CH3O-benzamide measured in this work (see Table 3) in a good agreement with the previous result measured with the isoperibolic combustion calorimeter25 by the same working group as for CH3-benzamides. To get more confidence in the experimental values, the weighted average values of ΔfHm ° (cr) were been calculated for each isomer of substituted benzamide (see Table 3; the uncertainty was taken as the weighing factor). These values were adopted for further thermochemical calculations. 3.5. Enthalpies of Fusion from Differential Scanning Calorimetry. The DSC results for 2-, 3-, and 4-CH3-benzamide measured in this work are given in Table 4, and they are compared there with enthalpies of fusion for CH3-benzamides reported by Almeida et al.24 Fusion enthalpies measured for CH3-benzamides in this work are in agreement with those from E


Article

The Journal of Physical Chemistry A Almeida et al.24 (see Table 4). Enthalpies of fusion for CH3Obenzamides are already reported by Almeida et al.25 (see Table 4). No solid−solid phase transitions before melting were observed for the benzamides under study. As a rule, enthalpies of fusion are ascribed to the melting temperature. However, for the thermochemical calculations these data should be adjusted to the reference temperature 298 K. The well-established general procedure22 based on the Kirchhoff equation (see Supporting Information) was applied. Uncertainties in the temperature adjustment of fusion enthalpies from Tfus to the reference temperature were assumed to amount to 30% of the total adjustment.22 Enthalpies of fusion adjusted to 298 K are useful for assessment of the internal consistency of the phase-change enthalpies of the benzamides under study. 3.6. Check of Internal Consistency of Phase-Change Enthalpies. The general thermochemical relationship: Δgl Hm◦ = Δcrg Hm° − Δ1cr Hm°

this work, we continue the development of this simple procedure based on a starting molecule with the well-established vaporization enthalpy. For example, the difference between vaporization enthalpies of CH3-benzene (toluene) and benzene provides the increment ΔH(H→CH3) for substitution of H atom on the benzene ring by the CH3 group. The difference between vaporization enthalpies of methoxybenzene and benzene provides the increment ΔH(H→CH3O) for substitution of the H atom on the benzene ring by the CH3O group. Our experiences with the halogen-substituted benzenes,11,43,44 naphthalenes, and anthracenes29 have shown that the increment ΔH(H→R) derived from substituted benzenes are generally transferable and can be used for calculation of vaporization enthalpies of different aromatic compounds. For the current study, it was reasonable to use the benzamide as the starting basic molecule for calculation of vaporization enthalpies of CH3- and ° (298 K) CH3O-substituted benzamides. The reliable value Δgl Hm = (85.4 ± 1.5) kJ·mol−1 for benzamide was recently measured by using the static method.27 Increments ΔH(H→CH3) and ΔH(H→CH3O) and the predicted theoretical values of substituted benzamides are listed in Tables 5 and 6.

(10)

connects phase-change enthalpies and helps to establish an internal consistency of the experimental data on the sublimation (Table 1), fusion (Table 4), and vaporization enthalpies (Tables 4). It should be mentioned that all enthalpies in eq 10 need to be referenced to the same temperature, for example, to the reference temperature 298 K. In this work, samples of 2- and 3-CH3Obenzamides were measured by the transpiration method in both ranges, above and below their melting temperature, to validate enthalpies of phase transitions according to eq 10. The value of ΔgcrH°m(298 K) = (110.4 ± 1.0) kJ·mol−1 for 2-CH3O-benzamide was derived in this work from vapor pressure measurements in the temperature range from 368.4 to 398.5 K. The vaporization enthalpy for 2-CH3O-benzamide Δgl H°m(298 K) = (89.4 ± 1.1) kJ·mol−1 was derived from transpiration measurements in the temperature range from 402.3 to 425.7 K. The enthalpy of fusion ΔlcrHm ° (298 K) = (21.6 ± 1.7) kJ·mol−1 for 2-CH3O-benzamide was calculated in Table 4 from the available fusion enthalpy reported at Tfus.25 The consistency of the experimental data measured in this work for 2-CH3O-benzamide is apparent from the comparison of the enthalpy of vaporization calculated according to eq 10 as the difference Δgl H°m(298 K) = ΔgcrH°m(298 K) − ΔlcrH°m(298 K) = 110.4−21.6 = (88.8 ± 2.0) kJ·mol−1 with the Δgl Hm ° (298 K) = (89.4 ± 1.1) kJ·mol−1 measured above the melting point in this work (see Table S12). The enthalpy of vaporization Δgl H°m(298 K) calculated from difference (ΔgcrH°m − ΔlcrHm) is in a good agreement (within the boundaries of experimental uncertainties) with those measured in this work for the liquid sample of 2-CH3O-benzamide. Our experimental results for the sublimation, vaporization, and fusion enthalpies for 2-CH3O-benzamide were shown to be consistent. We also used experimental sublimation, vaporization, and fusion enthalpies to validate the consistency of the phase-change enthalpies for 3-CH3O-benzamides successfully (see Tables 4 and S12). 3.7. Quick Assessment of Vaporization Enthalpies by Group Additivity. It is well-established that experimental sublimation enthalpies ΔgcrH°m do not obey the additivity rules, because the value of the molar enthalpy of sublimation encompasses two independent contributions: the molar enthalpy of vaporization Δgl Hm ° and the molar enthalpy of fusion ΔlcrHm °. Thus, any method of prediction of sublimation enthalpy suffers from a large uncertainty.40,41 In contrast, values of vaporization enthalpies readily obey the simple additive rules.42 In our previous work43,44 we have successfully applied an incremental approach to the halogen-substituted aromatic compounds. In

Table 5. Calculation of Enthalpies of Vaporization Δgl H°m (298 K) of Methylbenzamides by using Group Additivity Δgl H°m (298 K)/kJ·mol−1 basic molecule ΔH(H→CH3) theoretic value experimental value experimental value experimental value

benzamide CH3 2-CH3-benzamide 3-CH3-benzamide 4-CH3-benzamide

85.4 ± 1.5a 4.2 ± 0.1b 85.4 + 4.2 = 89.6 ± 1.5 90.7 ± 1.5c 89.5 ± 0.9c 91.4 ± 1.7c

a From ref 27. bDerived as a difference between Δgl Hm ° (298 K, CH3benzene) = 38.1 ± 0.1 kJ·mol−1 and Δgl H°m(298 K, benzene) = 33.9 ± 0.1 kJ·mol−1, reported in ref 45. cFrom Table 4.

Table 6. Calculation of Enthalpies of Vaporization Δgl H°m (298 K) of Methoxybenzamides by using Group Additivity Δgl H°m (298 K)/kJ·mol−1 basic molecule ΔH(H→CH3O) theoretic value experimental value experimental value experimental value

benzamide CH3O 2-CH3O-benzamide 3-CH3O-benzamide 4-CH3O-benzamide

85.4 ± 1.5a 12.5 ± 0.3b 85.4 + 12.5 = 97.9 ± 1.5 89.4 ± 1.1c 98.3 ± 1.3c 97.6 ± 2.4c

From ref 27. bDerived as a difference between Δgl H°m (298 K, CH3O° (298 K, benzene) = 46.4 ± 0.3 kJ·mol−1 reported in ref 46 and Δgl Hm benzene) = 33.9 ± 0.1 kJ·mol−1, reported in ref 45. cFrom Table 4. a

Comparison of the experimental and theoretical vaporization enthalpies shows the agreement on the level comparable with the typical experimental uncertainties of 1−2 kJ·mol−1. Following, this simple incremental group-additive procedure can be successfully used for the quick assesment of Δgl H°m(298 K) values for benzene derivatives with meta- and para-substitution of the benzene ring. However, values for the ortho-substituted derivatives should be either excluded or taken with caution. Indeed, the theoretical estimated enthalpy of vaporization of 2CH3-benzamide Δgl H°m(298 K) = (89.6 ± 1.5) kJ·mol−1 is occasionally close to the experimental value (90.7 ± 1.5) kJ· mol−1 (see Table 5), most probably due to the absence of significant steric repulsions of the small methyl substituent and F


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The Journal of Physical Chemistry A the bulkier amide group. Thus, this pattern could be useful for prediction of vaporization enthalpies of similarly shaped (e.g., ethyl, n-propyl, n-butyl, etc) ortho-substituted benzamides. However, prediction of vaporization enthalpy for 2-CH3Obenzamide with the slightly larger size of substituent failed (see Table 6), most probably due to the intramolecular hydrogen bonding in this molecule.25 Nevertheless, this simple and straightforward incremental procedure is useful for a quick appraisal of reliability of experimental vaporization enthalpies collected in comprehensive compilation by Chickos and Acree.47 Moreover, this procedure can be easily extended to assessment of reliability of sublimation enthalpies, ΔgcrH°m, according to eq 10, provided that the enthalpies of fusion enthalpies are calculated according to the Walden’s rule:39 Δcrl Hm◦ /Tfus = Walden constant

Figure 2. Optimized structures 2-CH3-benzamide obtained with the G4 method.

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As a matter of fact, for the broad scope of organic molecules the empirical Walden constant = 0.054 kJ·K−1·mol−1 was suggested irrespective to the structure of the molecule of interest. Having reliable experimental data on available Tfus and enthalpy of fusion the Walden constant at the level 0.06 kJ·K−1·mol−1 (see Table 4) was calculated for CH3- and CH3O-substituted benzamides. Thus, combination of the incremental group-additivity procedure for vaporization enthalpy with estimation of the fusion enthalpy can serve for the reasonable assessment of the level of sublimation collected in the extended compilation22 or for validation of new values appearing in the current literature. 3.8. Gas-State Enthalpies of Formation of Benzamides. Experimental data on the sublimation enthalpies and the solidstate formation enthalpies of the CH3- and CH3O-benzamides were used together for estimation of the gaseous standard molar enthalpies of formation, ΔfH°m(g) at 298 K (see Table 3, column 4). These values seem to be of impeccable quality, because they were independently measured in different laboratories, as well as they were successfully tested for internal consistency (see Tables 1 and 3). They can now be used for the validation of any quantum-chemical method. The composite method G43 was used in this work for estimation of the theoretical gas-phase enthalpies of formation for comparison with experimental data. An agreement between the experimental and theoretical results could provide a desired validation for both results and support the benchmark quality of thermochemical data for the benzamide derivatives studied in this work. We used the force-field method MM348 for initial search for stable conformers. Conformational analysis of meta- and parasubstituted CH3- and CH3O-benzamides has revealed vanishing small differences in energies of possible stable conformers. In contrast, for ortho-substituted CH3- and CH3O-benzamides at least two energetically different conformers were localized (see Figures 2 and 3). In agreement with the extended computational study of the 2-CH3O-benzamide,49 the most stable conformation of 2-CH3O-benzamide anticipates the intramolecular hydrogen bonding between one of the hydrogen atoms of the amide group and the oxygen atom of the methoxy group. Admittedly, the conformational studies of flexible molecules are important for correct calculation of ΔfH°m(g). However, from our experiences, only few most stable conformers usually contribute to the theoretical enthalpy of formation, provided that differences in their energies do not exceed 1−3 kJ·mol−1. Conformers with the energy difference greater than or equal to 7−10 kJ·mol−1 are practically not populated in the gas phase.50 This experience helps to reduce time-consuming calculations at a high level of theory, significantly.

Figure 3. Optimized structures 2-CH3O-benzamide obtained with the G4 method.

For the most stable conformers of the CH3- and CH3Obenzamides (see Figures 2 and 3), the enthalpies H298 were estimated by the G4 method, and they were converted to enthalpies of formation ΔfH°m(g, 298.15 K) with help of the atomization procedure as well as with the conventional ringconserved homodesmic reactions:

where R1 are the CH3− or CH3O− substituents. Using enthalpies of reaction 12 calculated from enthalpies H298 of benzamide derivatives (see Table S13) together with the enthalpies of formation ΔfHm ° (g) of benzene, toluene, anisole, and benzamide (see Table S14), theoretical enthalpies of formation of all isomeric CH3- and CH3O-benzamides were calculated (see Table 3, column 5). Theoretical enthalpies of formation of all benzamide derivatives calculated via reaction 12 are in excellent agreement with the experimental values, proving the benchmark quality of thermochemical data for the benzamide derivatives evaluated in this work. To our surprise, the theoretical enthalpies of formation of all isomeric CH3- and CH3Obenzamides calculated via the atomization procedure are also in very good agreement with the evaluated experimental data set (see Table S15). Such a close agreement is in contrast to the recent general observation that the G4 method combined with the atomization procedure (G4-AT) underestimates the ΔfH°m(g) values for most nitro compounds by up to 20 kJ· mol−1, and their conclusion that reliable results cannot be expected when using the atomization reaction4,5 seems to not always be correct. To get more information on G4-AT G


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Table 7. Comparison of Evaluated Experimental Enthalpies of Formation of Amides with Theoretical Values from G4-Atomization Procedure (in kJ·mol−1) ΔfH°m(g)/298 K exp compound

° (g) G4-AT ΔfHm

formula

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formamide acetamide N-methyl-formamide N,N-dimethyl-formamide N,N-dimethyl-acetamide butanamide 2-methyl-propanamide 2,2-dimethyl-propanamide benzamide N-phenyl-acetamide N,N-diacetyl-acetamide N-(4-hydroxyphenyl)-acetamide

CH3NO C2H5NO C2H5NO C3H7NO C4H9NO C4H9NO C4H9NO C5H11NO C7H7NO C8H9NO C6H9NO3 C8H9NO2

2-methylbenzamide 3-methylbenzamide 4-methylbenzamide 2-methoxylbenzamide 3-methoxylbenzamide 4-methoxylbenzamide

C8H9NO C8H9NO C8H9NO C8H9NO2 C8H9NO2 C8H9NO2

−188.6 ± 0.4 −238.3 ± 0.9c −191.2 ± 2.0c −192.4 ± 1.6c −228.1 ± 1.8c −279.1 ± 0.9c −282.6 ± 0.9c −313.1 ± 1.4c −99.8 ± 0.6d −108.0 ± 2.0e −280.5 ± 1.9f −550.1 ± 1.3g this work −128.7 ± 1.7 −132.8 ± 1.6 −136.7 ± 1.5 −255.5 ± 1.5 −255.3 ± 1.7 −257.4 ± 1.8

b

Δa

−188.9 −233.9 −187.6 −194.0 −228.4 −276.9 −282.1 −312.2 −98.9 −107.4 −279.7 −553.7

0.3 ± 0.4 −4.4 ± 0.9 −3.6 ± 2.0 1.6 ± 1.6 0.3 ± 1.8 −2.2 ± 0.9 −0.5 ± 0.9 −0.9 ± 1.4 −0.9 ± 0.6 −0.6 ± 2.0 −0.8 ± 1.9 3.6 ± 1.3

−128.1 −133.0 −133.4 −257.0 −256.9 −256.9 average from 17 entries

−0.6 ± 1.7 0.2 ± 1.6 −3.3 ± 1.5 1.5 ± 1.5 1.6 ± 1.7 −0.5 ± 1.8 ±1.4

a Uncertainties are the same as by experimental data. bTaken from ref 52. cTaken from ref 7. dTaken from refs 27 and 38. eTaken from refs 53 and 54. fTaken from ref 55. gTaken from ref 56.

commonly used for testing quantum-chemical methods, consists mostly of small or middle-size molecules. In this study, we deliberately restricted our selection of amides with species containing not more than 11 heavy atoms. On the one hand, this choice is stipulated by the size of majority of molecules presented in G3/05 set. On the other hand, the available experimental data ° (g) values for larger molecules are as a rule significantly on ΔfHm less reliable due to simple reasons like insufficient purity attestation of the sample or even due to complications in vaporization/sublimation studies of low volatile compounds. It is self-evident that the set of anchor molecules selected and presented in Table 7 is too small for the global conclusions, and it must be significantly extended with thermochemically evaluated ΔfH°m(g) values (separate evaluation of sublimation/vaporization enthalpies and ΔfH°m(liq or cr) values) to ascertain the reliability of the G4-AT procedure for larger molecules.

performance we collected a restricted but reliable set of the experimental data on differently shaped amides (see Table 7, column 3). Our selection was mostly based on experimental ΔfH°m(g) values evaluated7 with help of the group-additivity procedure. One of the best flags to possible experimental errors is a large discrepancy between experimental and calculated values− especially if other, closely related compounds show no such discrepancy.51 Moreover, some recent experimental thermochemical data52−56 on amides were also added to the selected set (see Table 7, column 3). Together with the CH3- and CH3Obenzamides the test set contained 17 aliphatic and aromatic amides with evaluated experimental ΔfH°m(g) values. Theoretical enthalpies of formation from G4-AT calculations are given in Table 7, column 4. Differences between the experimental and theoretical values are listed in Table 7, column 5. Before starting with discussion of these differences, it should be mentioned that typical experimental uncertainties of experimental ΔfHm ° (g) values for the nitrogen-containing compounds are on the level of 1−2 kJ·mol−1; moreover, the accuracy of the G4-AT procedure is claimed to be at the level of ∼3.5 kJ·mol−1. In spite of such expanded uncertainties, most of the differences in column 5 are at the level of 1 kJ·mol−1 and even lower! The average uncertainty of 1.4 kJ·mol−1 was calculated for this small set of 17 molecules having well-established thermochemical data. A few important conclusions can be drawn from the observed remarkable agreement between theoretical and experimental values. First of all, the G4-AT procedure seems to be the easy and reliable way to convert the high-level enthalpies H298 into ΔfH°m(g) values for the C, H, N, O-containing molecules. This procedure evidently works for the aliphatic and aromatic amides, but this procedure must be analyzed and carefully validated for other homologues series and groups of structurally related molecules, where reliable thermochemical data are available. The second important aspect is the size of molecules involved in the G4-AT procedure. As a matter of fact, the G3/05 set, which is

4. CONCLUSIONS Careful evaluation of the thermochemical properties of isomeric CH3- and CH3O-substituted benzamides have been performed based on the additional experimental results. Experimental values of ΔgcrH°m(298 K), ΔlcrH°m(298 K), Δgl H°m(298 K), and ΔfH°m(cr, 298 K) were evaluated and tested for internal consistency. A simple incremental group-additivity procedure was suggested for a quick assessment of vaporization enthalpies of substituted benzamides. Mutual validation of the theoretical and experimental ΔfH°m(g, 298 K) was performed with the high-level G4 composite quantum-chemical method. A remarkable ability of the atomization procedure to convert the G4 enthalpies H298 into ΔfH°m(g) values has been established for the set of aliphatic and aromatic amides. Further outlook for the proper validation of the G4-AT procedure was discussed. H


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Biologically Relevant Adenine and Cytosine. A Combined Experimental and Theoretical Study. J. Phys. Chem. A 2015, 119, 9680−9691. (2) Emel'yanenko, V. N.; Yermalayeu, A. V.; Voges, M.; Held, C.; Sadowski, G.; Verevkin, S. P. Thermodynamics of a Model Biological Reaction: A Comprehensive Combined Experimental and Theoretical Study. Fluid Phase Equilib. 2016, 422, 99−110. (3) Curtiss, L. A.; Redfern, P. C.; Raghavachari, K. Gaussian-4 Theory. J. Chem. Phys. 2007, 126, 084108. (4) Dorofeeva, O. V.; Kolesnikova, I. N.; Marochkin, I. I.; Ryzhova, O. N. Assessment of Gaussian-4 Theory for the Computation of Enthalpies of Formation of Large Organic Molecules. Struct. Chem. 2011, 22, 1303−1314. (5) Suntsova, M. A.; Dorofeeva, O. V. Use of G4 Theory for the Assessment of Inaccuracies in Experimental Enthalpies of Formation of Aromatic Nitro Compounds. J. Chem. Eng. Data 2016, 61, 313−329. (6) Simmie, J. M. A Database of Formation Enthalpies of Nitrogen Species by Compound Methods (CBS-QB3, CBS-APNO, G3, G4). J. Phys. Chem. A 2015, 119, 10511−10526. (7) Verevkin, S. P. Improved Group-Additivity Values for the Estimation of the Standard Enthalpies of Formation of Imines and Carboxylic Acids Derivatives. J. Therm. Anal. Calorim. 2000, 60, 437− 451. (8) Verevkin, S. P.; Zaitsau, D. H.; Emel’yanenko, V. N.; Stepurko, E. N.; Zherikova, K. V. Benzoic Acid Derivatives: Evaluation of Thermochemical Properties with Complementary Experimental and Computational Methods. Thermochim. Acta 2015, 622, 18−30. (9) Kulikov, D.; Verevkin, S. P.; Heintz, A. Determination of Vaporization Enthalpies of the Aliphatic Branched C5 and C6 Alcohols from Transpiration Method. J. Chem. Eng. Data 2001, 46, 1593−1600. (10) Verevkin, S. P.; Emel'yanenko, V. N. Transpiration Method: Vapor Pressures and Enthalpies of Vaporization of Some Low-Boiling Esters. Fluid Phase Equilib. 2008, 266, 64−75. (11) Verevkin, S. P.; Sazonova, A. Yu.; Emel'yanenko, V. N.; Zaitsau, D. H.; Varfolomeev, M. A.; Solomonov, B. N.; Zherikova, K. V. Thermochemistry of Halogen-Substituted Methylbenzenes. J. Chem. Eng. Data 2015, 60, 89−103. (12) Emel'yanenko, V. N.; Verevkin, S. P. Benchmark Thermodynamic Properties of 1,3-Propanediol: Comprehensive Experimental and Theoretical Study. J. Chem. Thermodyn. 2015, 85, 111−119. (13) Sabbah, R.; Xu-Wu, A.; Chickos, J. S.; Planas Leitao, M. L.; Roux, M. V.; Torres, L. A. Reference Materials for Calorimetry and Differential Thermal Analysis. Thermochim. Acta 1999, 331, 93−204. (14) Zaitseva, K. V.; Varfolomeev, M. A.; Novikov, V. B.; Solomonov, B. N. Enthalpy of Cooperative Hydrogen Bonding in Complexes of Tertiary Amines with Aliphatic Alcohols: Calorimetric Study. J. Chem. Thermodyn. 2011, 43, 1083−1090. (15) Zaitseva, K. V.; Varfolomeev, M. A.; Solomonov, B. N. Thermodynamic Functions of Hydrogen Bonding of Amines in Methanol Derived from Solution Calorimetry Data and Headspace Analysis. Thermochim. Acta 2012, 535, 8−16. (16) Verevkin, S. P.; Schick, C. Substituent Effects on the Benzene Ring. Determination of the Intra-Molecular Interactions of Substituents in tert-Alkyl Substituted Catechols from Thermochemical Measurements. J. Chem. Eng. Data 2000, 45, 946−952. (17) Emel’yanenko, V. N.; Verevkin, S. P.; Heintz, A. The Gaseous Enthalpy of Formation of the Ionic Liquid 1-Butyl-3-Methylimidazolium Dicyanamide from Combustion Calorimetry, Vapor Pressure Measurements, and Ab Initio Calculations. J. Am. Chem. Soc. 2007, 129, 3930−3937. (18) Hubbard, W. N.; Scott, D. W.; Waddington, G. Experimental Thermochemistry; Rossini, F.D., Ed.; Interscience Publishers: New York, 1956; pp 75−127. (19) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A. et al. Gaussian 09, Revision A.02; Gaussian Inc: Wallingford, CT, 2009. (20) Verevkin, S. P.; Emel'yanenko, V. N.; Notario, R.; Roux, M. V.; Chickos, J. S.; Liebman, J. F. Rediscovering the Wheel. Thermochemical

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpca.6b08027. Origin, purity, methods of purification, and analysis of chemicals used in this work. Results from transpiration method: absolute vapor pressures p, standard molar sublimation enthalpies, and standard molar sublimation entropies. Experimental enthalpies of solution of substituted benzamides in acetonitrile measured in this work at 298.15 K and 0.1 MPa. Formula, density ρ (T = 293 K), specific heat capacity cp (T = 298 K), and expansion coefficients (δV/δT)p of the materials used in the present study. Results for combustion experiments at T = 298.15 K (p° = 0.1 MPa) for the 2-CH3-benzamide. Results for combustion experiments at T = 298.15 K (p° = 0.1 MPa) for the 3-CH3-benzamide. Results for combustion experiments at T = 298.15 K (p° = 0.1 MPa) for the 4-CH3benzamide. Results for combustion experiments at T = 298.15 K (p° = 0.1 MPa) for the 2-CH3O-benzamide. Compilation of data on molar heat capacities C°p,m (in J· K−1·mol−1) at 298.15 K. Compilation of vapor pressures used for the joint treatment according to eq 3. Coefficients of eq 3 for calculation of vapor pressures over solid benzamides. Enthalpies of vaporization Δgl H°m of benzamides. The G4 total energies at 0 K and enthalpies at 298.15 K (in hartree) of the molecules studied in this work. Thermochemical data at T = 298 K (p° = 0.1 MPa) for reference compounds. Comparison of experimental and G4-calculated enthalpies of formation of benzamides. Experimental vapor pressures of the 2-CH3-benzamide. Experimental vapor pressures of the 3-CH3-benzamide, 4CH3-benzamide, 2-CH3O-benzamide, 3-CH3O-benzamide, and 4-CH3O-benzamide. (PDF)

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AUTHOR INFORMATION

Corresponding Authors

*For the solution calorimetry experiments (Kazan) and correlations, e-mail B. N. Solomonov: boris.solomonov@kpfu. ru. Phone:+7-8432-233-73-46. *For the combustion, vaporization/sublimation experiments (Rostock), data evaluation, and correlations, e-mail S. P. Verevkin: [email protected]. Phone: +49-381498-6508. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS K.V.Z. gratefully acknowledges a research scholarship from Deutsche Akademische Austauschdienst. This work has been supported by the German Science Foundation in frame of the priority program SPP 1708 “Material Synthesis Near Room Temperature”. This work has been partly supported by the Russian Government Program of Competitive Growth of Kazan Federal University and Russian Foundation for Basic Research No. 15-03-07475. B.S. gratefully acknowledges the financial support by the Russian Ministry of Education and Science.

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REFERENCES

(1) Emel'yanenko, V. N.; Zaitsau, D. H.; Shoifet, E.; Meurer, F.; Verevkin, S. P.; Schick, C.; Held, C. Benchmark Thermochemistry for I


Article

The Journal of Physical Chemistry A Analysis of Energetics of the Aromatic Diazines. J. Phys. Chem. Lett. 2012, 3, 3454−3459. (21) McQuarrie, D. A. Statistical Mechanics; Harper’s chemistry series; Harper & Row: New York, 1976. (22) Chickos, J. S.; Acree, W. E., Jr Enthalpies of Sublimation of Organic and Organometallic Compounds. 1910−2001. J. Phys. Chem. Ref. Data 1999, 31, 537−698. (23) Chickos, J. S.; Hosseini, S.; Hesse, D. G.; Liebman, J. F. Heat Capacity Corrections to a Standard State: a Comparison of New and Some Literature Methods for Organic Liquids and Solids. Struct. Chem. 1993, 4, 271−277. (24) Almeida, A. R. R. P.; Matos, M. A. R.; Monte, M. J. S.; Morais, V. M. F. Experimental and Computational Thermodynamic Study of ortho-, meta-, and para-Methylbenzamide. J. Chem. Thermodyn. 2012, 47, 81−89. (25) Almeida, A. R. R. P.; Monte, M. J. S.; Matos, M. A. R.; Morais, V. M. F. The Thermodynamic Stability of the Three Isomers of Methoxybenzamide: An Experimental and Computational Study. J. Chem. Thermodyn. 2014, 73, 12−22. (26) Clarke, E. C. W.; Glew, D. N. Evaluation of Thermodynamic Functions from Equilibrium Constants. Trans. Faraday Soc. 1966, 62, 539−547. (27) Almeida, A. R. R. P.; Monte, M. J. S. Thermodynamic Study of Benzamide, N-Methylbenzamide, and N,N-Dimethylbenzamide: Vapor Pressures, Phase Diagrams, and Hydrogen Bond Enthalpy. J. Chem. Eng. Data 2010, 55, 3507−3512. (28) Solomonov, B. N.; Varfolomeev, M. A.; Nagrimanov, R. N.; Novikov, V. B.; Zaitsau, D. H.; Verevkin, S. P. Solution Calorimetry As A Complementary Tool for the Determination of Enthalpies of Vaporization and Sublimation of Low Volatile Compounds at 298.15 K. Thermochim. Acta 2014, 589, 164−173. (29) Solomonov, B. N.; Varfolomeev, M. A.; Nagrimanov, R. N.; Novikov, V. B.; Ziganshin, M. A.; Gerasimov, A. V.; Verevkin, S. P. Enthalpies of Vaporization and Sublimation of the Halogen-Substituted Aromatic Hydrocarbons at 298.15 K: Application of Solution Calorimetry Approach. J. Chem. Eng. Data 2015, 60, 748−761. (30) Varfolomeev, M. A.; Novikov, V. B.; Nagrimanov, R. N.; Solomonov, B. N. Modified Solution Calorimetry Approach for Determination of Vaporization and Sublimation Enthalpies of Branched-Chain Aliphatic and Alkyl Aromatic Compounds at 298.15 K. J. Chem. Thermodyn. 2015, 91, 204−210. (31) Solomonov, B. N.; Varfolomeev, M. A.; Nagrimanov, R. N.; Novikov, V. B.; Buzyurov, A. V.; Fedorova, Y. V.; Mukhametzyanov, T. A. New Method for Determination of Vaporization and Sublimation Enthalpy of Aromatic Compounds at 298.15 K Using Solution Calorimetry Technique and Group-Additivity Scheme. Thermochim. Acta 2015, 622, 88−96. (32) Solomonov, B. N.; Nagrimanov, R. N.; Mukhametzyanov, T. A. Additive Scheme for Calculation of Solvation Enthalpies of Heterocyclic Aromatic Compounds. Sublimation/Vaporization Enthalpy at 298.15 K. Thermochim. Acta 2016, 633, 37−47. (33) Nagrimanov, R. N.; Solomonov, B. N.; Emel'yanenko, V. N.; Verevkin, S. P. Six-membered ring aliphatic compounds: a search for regularities in phase transitions. Thermochim. Acta 2016, 638, 80−88. (34) Emel'yanenko, V. N.; Nagrimanov, R. N.; Solomonov, B. N.; Verevkin, S. P. Adamantanes: Benchmarking of Thermochemical Properties. J. Chem. Thermodyn. 2016, 101, 130−138. (35) Cox, J. D.; Wagman, D. D.; Medvedev, V. A. CODATA Key Values for Thermodynamics; Hemisphere Publishing Corp: New York, 1989. (36) Olofsson, G. Assignment of Uncertainties. In Combustion Calorimetry; Sunner, S., Månsson, M., Eds.; Pergamon Press, 1979; pp 137−159. (37) Wieser, M. E.; Holden, N.; Coplen, T. B.; Bohlke, J. K.; Berglund, M.; Brand, W. A.; De Bievre, P.; Groning, M.; Loss, R. D.; Meija, J.; Hirata, T.; Prohaska, T.; Schoenberg, R.; O’Connor, G.; Walczyk, T.; Yoneda, S.; Zhu, X. K. Atomic Weights of the Elements 2011 (IUPAC technical report). Pure Appl. Chem. 2013, 85, 1047−1078. (38) Steele, W. V.; Chirico, R. D.; Nguyen, A.; Hossenlopp, I. A.; Smith, N. K. Determination of Ideal-Gas Enthalpies of Formation for

Key Compounds. Am. Inst. Chem. Eng. Symp. Ser. (AIChE Symp. Ser.) 1990, 138−154. (39) Gilbert, A. S. Entropy-Enthalpy Compensation in the Fusion of Organic Molecules: Implications for Walden’s Rule and Molecular Freedom in the Liquid State. Thermochim. Acta 1999, 339, 131−142. (40) Emel'yanenko, V. N.; Kabo, G. J.; Verevkin, S. P. Measurement and Prediction of Thermochemical Properties. Improved Increments for the Estimation of Enthalpies of Sublimation and Standard Enthalpies of Formation of Alkyl Derivatives of Urea. J. Chem. Eng. Data 2006, 51, 79−87. (41) Salahinejad, M.; Le, T. C.; Winkler, D. A. Capturing the Crystal: Prediction of Enthalpy of Sublimation, Crystal Lattice Energy, and Melting Points of Organic Compounds. J. Chem. Inf. Model. 2013, 53, 223−229. (42) Verevkin, S. P.; Emel'yanenko, V. N.; Diky, V.; Muzny, C. D.; Chirico, R. D.; Frenkel, M. New Group Contribution Approach to Thermochemical Properties of Organic Compounds: Hydrocarbons and Oxygen Containing Compounds. J. Phys. Chem. Ref. Data 2013, 42, 033102. (43) Verevkin, S. P.; Emel'yanenko, V. N.; Klamt, A. Thermochemistry of Chlorobenzenes and Chlorophenols: Ambient Temperature Vapor Pressures and Enthalpies Phase Transitions. Experiment and Calculations. J. Chem. Eng. Data 2007, 52, 499−510. (44) Verevkin, S. P.; Melkhanova, S. V.; Emel'yanenko, V. N.; Varfolomeev, M. A.; Solomonov, B. N.; Zherikova, K. V. Thermochemistry of Dihalogen-Substituted Benzenes: Data Evaluation Using Experimental and Quantum Chemical Methods. J. Phys. Chem. B 2014, 118, 14479−14492. (45) Roux, M. V.; Temprado, M.; Chickos, J. S.; Nagano, Y. Critically Evaluated Thermochemical Properties of Polycyclic Aromatic Hydrocarbons. J. Phys. Chem. Ref. Data 2008, 37, 1855−1996. (46) Simões, R. G.; Agapito, F.; Diogo, H. P.; Minas da Piedade, M. E. The Enthalpy of Formation of Anisole: Implications for the Controversy on the O−H Bond Dissociation Enthalpy in Phenol. J. Phys. Chem. A 2014, 118, 11026−11032. (47) Chickos, J. S. Enthalpies of Vaporization of Organic and Organometallic Compounds, 1880−2002. J. Phys. Chem. Ref. Data 2003, 32, 519. (48) Allinger, N. L.; Yuh, Y. H.; Lii, J. H. Molecular mechanics. The MM3 Force Field for Hydrocarbons. J. Am. Chem. Soc. 1989, 111, 8551− 8566. (49) Aarset, K.; Page, E. M.; Rice, D. A. Hydrogen Bonding in the GasPhase: The Molecular Structures of 2-Hydroxybenzamide (C7H7NO2) and 2-Methoxybenzamide (C8H9NO2), Obtained by Gas-Phase Electron Diffraction and Theoretical Calculations. J. Phys. Chem. A 2013, 117, 3034−3040. (50) Verevkin, S. P.; Emel'yanenko, V. N.; Garist, I. V. Benchmark Thermodynamic Properties of Alkanediamines: Experimental and Theoretical Study. J. Chem. Thermodyn. 2015, 87, 34−42. (51) Roganov, G. N.; Pisarev, P. N.; Emel'yanenko, V. N.; Verevkin, S. P. Measurement and Prediction of Thermochemical Properties. Improved Benson-type Increments for the Estimation of Enthalpies of Vaporization and Standard Enthalpies of Formation of Aliphatic Alcohols. J. Chem. Eng. Data 2005, 50, 1114−1124. (52) Emel'yanenko, V. N.; Verevkin, S. P.; Varfolomeev, M. A.; Turovtsev, V. V.; Orlov, Yu. D. Thermochemical Properties of Formamide Revisited: New Experiment and Quantum Mechanical Calculations. J. Chem. Eng. Data 2011, 56, 4183−4187. (53) Perlovich, G. L.; Volkova, T. V.; Bauer-Brandl, A. Towards an Understanding of the Molecular Mechanism of Solvation of Drug Molecules: a Thermodynamic Approach by Crystal Lattice Energy, Sublimation, and Solubility Exemplified by Paracetamol, Acetanilide, and Phenacetin. J. Pharm. Sci. 2006, 95, 2158−2169. (54) Ribeiro da Silva, M. A. V.; Pilcher, G.; Santos, L. M. N. B. F.; Spencer, L. M.; Lima, S. Calibration and Test of an Aneroid Mini-Bomb Combustion Calorimeter. J. Chem. Thermodyn. 2007, 39, 689−697. (55) Hill, J. O.; Wadso, I. Some Thermochemical Properties of N,N,NTriacetylammonia. Acta Chem. Scand. 1968, 22, 1590−1594. J


Article

The Journal of Physical Chemistry A (56) Picciochi, R.; Diogo, H. P.; Minas da Piedade, M. E. Thermochemistry of Paracetamol. J. Therm. Anal. Calorim. 2010, 100, 391−401.

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